1. Field of the Invention
The present invention relates to a recording medium and a recording device and, more particularly, to a recording disk of 0.5 xcexcm or below in track width or track pitch, and a recording device for recording information on the recording disk.
2. Description of the Related Art
Recently, computerized society has made remarkable advancement and there has been a demand for the development of techniques that enables the storage of an increased information volume. Efforts are being made in the field of researches into disk type file memories for the reduction of the diameter of recording bits and the length of recording tracks. It is expected that track length for magnetic recording will shrink from its present length of about 2 xcexcm to 1 xcexcm in the year 2000 and to 0.5 xcexcm or below in the year 2005. A sample servo method is used for magnetic recording, and a sample servo method using V-grooves is used for optical recording. The former does not use any guide grooves, while the latter uses guide grooves, in which recording bits are formed between the adjacent guide grooves. When tracks of 0.5 xcexcm or below in track length or track pitch are used for ultrahigh-density recording, the nonrepeatable radial positioning error in a disk rotating mechanism is large and the sample servo method can not be used. The recording medium for optical recording has recording bits formed between the adjacent guide grooves.
A high-density read-only memory (ROM) using techniques concerning an atomic force microscope (AFM) disclosed in Physical Review Letters, Vol. 56, pp. 930 to 933 (1986) is proposed in Appl. Phys. Lett., Vol. 69, pp. 4262 to 4264 (1996). This ROM is formed on a recording disk provided with recording tracks arranged at a track pitch of 0.1 xcexcm. The recording disk is not provided with any guide grooves and is provided with only concave recording bits.
The conventional recording disks without any guide grooves or those provided with guide grooves and recording bits formed between the adjacent guide grooves have the following problems.
When a recording disk of 0.5 xcexcm below in track length or track pitch is used for ultrahigh-density recording, a tracking control system is affected by the nonrepeatable radial positioning error in a disk rotating mechanism. It is said that nonrepeatable radial positioning error in the operation of a disk rotating mechanism employing ball bearings is about 200 nm, while the same in the operation of a disk rotating mechanism employing liquid bearings is in the range of about 50 to 20 nm. Accordingly, it is said that a practical maximum track length for the sample servo system is about 10 times the nonrepeatable radial positioning error. If track length is 0.5 xcexcm or below the sample servo system is infeasible and a continuous servo system must be used.
The guide grooves of a disk having recording bits formed between the adjacent guide grooves, such as a disk for optical recording, are useless spaces and it is important to eliminate such useless spaces.
Accordingly, it is an object of the present invention to solve the technical problems in the prior art and to provide a recording medium that enables tracking of 0.5 xcexcm or below.
Another object of the present invention is to provide a recording device using the recording medium of the present invention.
With the foregoing object in view, the present invention provides a recording medium, such as a recording disk, provided with guide grooves for controlling the position of a recording head, and recording bits formed in the guide grooves for high-density recording. Thus, the recording disk of the present invention is provided in its major surface with guide grooves for controlling the position of a probe (head), and recording bits formed in the guide grooves, in which the guide grooves are 0.5 xcexcm or below in width and 0.5 xcexcm or below in pitch. The recording bits may be concave or convex with respect to a direction perpendicular to the guide grooves, and the center of the recording bits may coincide with the center of the guide grooves, the center of the recording bits may be dislocated from the center of the guide grooves, the recording bits may be different in depth from the guide grooves, and the recording bits may have a diameter different from the width of the guide grooves.
The present invention provides also a recording device for driving the recording medium as mentioned above, provided with a disk rotating mechanism employing ball bearings or liquid bearings.
A recording device in accordance with the present invention is able to write data to a recording disk according to the present invention at a track length of 0.5 xcexcm or below. The recording device is a high-density recording device employing an AFM as a recording head. Lateral forces acting on a probe included in a recording head are measured and the probe is controlled by a servocontrol system for tracking control so as to lie on the center of the guide groove. In the recording disk, the width Ws of the recording bits is greater than the width Wg of the guide grooves. Therefore, the probe is able to identify the recording bits through the detection of an atomic force perpendicularly acting on the probe. The depth of sinking of the probe into the guide groove when the probe travels along the guide groove is less than that of sinking of the probe into the recording bit. When the depth of sinking of the probe into the guide groove increases by an increment corresponding to the difference between the depth of sinking of the probe into the recording bit and that into the guide groove when the probe moves from the guide groove into the recording bit, a recording signal is provided. Thus, information can be erased, and written to or read from a desired position without being affected by nonrepeatable radial positioning error even if a conventional drive system employing ball bearings or liquid bearings is used, if the recording disk of the present invention is used. The use of the recording disk of the present invention improves the reliability of ultrahigh-density recording.
The recording disk of the present invention enables ultrahigh-density recording in a high recording density of 1 Tbit (1012 bits)/in.2.